Heretofore in sealing two separate pieces of a wellhead that are fixed together, an annular rubber seal means has been placed between portions of the two pieces of wellhead and then subjected to compression forces between the two pieces of wellhead so that the elastic seal means expands into sealing engagement with both pieces of wellhead.
Normally the wellhead is put together and the seal means compressed at a given temperature. Thereafter the wellhead is put into operation, at which time the temperature of the seal means often increases. This increase in operating temperature helps the efficiency of the seal means. However, should the well be shut in and production stopped, the temperature of the seal means can drop below the initial makeup temperature at which the wellhead was put together in the first place. This can have an adverse effect on the seal means since it tends to contract on cooling, particularly if the wellhead is emplaced in a far North location such as the Arctic or similar locations. When the seal means is cooled substantially below the initial wellhead makeup temperature, the seal can release in some situations thereby allowing leaks from the interior of the wellhead to its exterior.